Open-hearth furnace



Dec. m, 1949 F. s. BLOOM 2,491,705

OP EN-HEARTH FURNACE 2 Sheets-Sheet 2 Filed Feb. 24, 1949 INVENTORFREDERICK S. BLOOM Patented Dec. 2c, 1949 DPEN-HEARTH FURNACE FrederickS. Bloom, Mount Lebanon Township, Allegheny County, Pa.

Application February 24, 1949, Serial No. 78,180

a Dias. (oi. 263-l) This invention relates to means for heating an openhearth regenerative furnace either with gas alone or with oil alone.Natural or coke oven gas is generally a less expensive fuel than oil andis therefore desirable for the purpose of heating large open hearthfurnaces such as those used for making steel. However, the supply of gasis sometimes out oh and it is highly desirable to avoid a shut-down byusing some other fuel. While gas-fired open hearth furnaces and oiliiredopen hearth furnaces are well known in the art and mixtures of gas andoil have been used in both gas-fired and oil-fired furnaces, it has notheretofore been practicable to use gas alone and oil alone alternativelyin any one furnace. The problem is to get a proper flame to heat thecharge in the melting chamber and at the same time to avoid burning outthe furnace lining, particularly the roof lining of the furnace.

A conventional open hearth furnace designed to be heated by oil has acomparatively straight roof and passages of substantially uniformcrosssection connected to the ports at either sides of the furnace. itsingle burner is mounted at each end of the furnace. Gas can be mixedwith the oil to some extent but if straight gas is used in either of theburners it has been found that turbulence in the port eliminates theluminosity of the flame and reduces the roof life very substantially.For example, the use of straight gas in a furnace designed for oil hasreduced the roof life to approximately 100 heats as compared with 225250heats when oil was used.

A conventional open hearth furnace designed to be heated by gas, on theother hand, has a downwardly extending knuckle in-the roof of thefurnace adjacent each port at either end of the furnace. The passagesleading to the ports slope downwardly and progressively narrow as theyapproach the ports in order to accelerate the speed of the incoming airbefore it enters the melting chamber. Gas is fed into the passage atrelatively low pressure and velocity and the accelerated stream ofincoming air serves to direct the naming gas downwardly into the meltingchamher. It is not practicable to introduce straight oil through gasburners and if a conventional single oil burner is inserted at each endof a gasflred furnace it has been found that the flame from the oilburner tends to burn away the roof,

thereby greatly reducing the life of the furnace.

My invention makes it possible to heat an open hearth furnace ofgas-fired design selectively with gas alone or oil alone andwithoutsuffering the dvantages mentioned above. My invention E will best beunderstood by reference to the following detailed description andin theaccompanying drawings. I have shown inthe drawings. for purposes ofillustration only, a present preferred embodiment of my invention, inwhich Figure 1 is a sectional side view of one end. of a preferredembodiment of my open hearth furnace (on the line I--I in Figure 2)Figure 2 is a sectional plan view on. the line II-II in Figure 1;

Figure 3 is a partially sectioned plan view of one of the oil burners ofmy furnace;

Figure 4 is a sectional view on the line Ill-JV in Figure 3;

Figure 5 is a sectional view on the line V- -V in Figure 3; and

Figure 6 is a diagrammatic plan view of the fuel oil and steam supplysystem for the oil burners at each end of my furnace.

My furnace is of the regenerative type in which the flow ofair throughthe furnace is reversed periodically in the conventional manner and thetwo ends of the furnace are therefore symmetrical in all respects,including the arrangement of burners. One end of my furnace isillustrated in Figures 1 and 2. A central furnace chamber it containsthe charge to be melted (not shown) and has a hearth l I, a roof if, aport l3 and a downwardly extending knuckle M adjacent the upper portionof the port it. A passage to slopes downwardly and narrows as itapproaches the port it and is connected to an iair uptake it from achecker chamber (not shown). The air uptake it is also connected to astack (not shown) in order to exhaust products of combustion when theregenerative cycle is reversed. Water-jacketed gas burners Ill and itare set into the side walls l9 and 20 of the passage l5 and areconnected to gas supply lines Ma and Mia controlled by valves ill) anditb, respectively. A bafile ti extends above the level (if the gasburners ill and i8 where the passage iii connects with the air uptakeit. The construction so far described is conventional in regenerativeopen hearth furnaces designed to be heated by natural or coke oven gas.

My furnace also has oil burners 22 and 23 positioned within the passagel5 below the level of the knuckle M. As shown in Figure 2, these oilburners are positioned adjacent and on the approximate level of the gasburners ii and i8 respectively, between the gas burners l1 and i0 andthe port l3. The construction of the oil burners is substantially thesame in each case, the burner .23 being illustrated in detail in Figures3-5. A cylindrical water jacket 24 having an outer wall 25 and an innerwall 26 surrounds and is spaced from a pipe 21 through which a mixtureof oil and high-pressure steam is fed into the burner. The pipe 21terminates in a nozzle 28 arranged to project the mixture of oil andsteam in a conical stream out of the burner through an opening 29 in thewater jacket 24. The water jacket 24 has a water inlet 30, a wateroutlet 3| and a dividing wall 3Ia to form passages through which wateris circulated to cool the oil burner. The pipe 2! is connected throughintermediate connections 32 to an oil supply line 33 and a steam supplyline 34I The oil burners 22 and 23 are slidably mounted in the sidewalls I9 and 20 of the burners and are withdrawn through the said sidewalls when the furnace is to be heated with gas instead of oil. Theintermediate connections 32 are disconnected when the oil burners 22 and23 are withdrawn. As shown in Figure 3, the burner 23 has a flange 35around its outer end which projects outside of the furnace. The flangeis bolted to the furnace when the oil burners are in operation and itsbolt holes 36 are elongated so that the burner may be rotated to adjustthe angle of fire of its nozzle within the furnace.

The supply line system for the oil burners of my furnace is illustrateddiagrammatically in Figure 6. The burner 23 described above has a valve31 controlling its fuel oil supply line 33 and a valve 38 controllingits steam supply line 34. The burner 22 similarly has a fuel oil supplyline 39 controlled by a valve 40 and a steam supply line 4i controlledby a valve 42. Oil burners of similar construction are similarlypositioned at the opposite end of the furnace and these burners,designated 43 and 44 are respectively connected to fuel oil supply lines45 and 46 controlled by valves 41 and 48 and to steam supply lines 49and controlled by valves 5| and 52. The fuel lines 33, 39, 45 and 46 areall connected to a main fuel oil supply line 53 with an intermediatevalve 54 controlling the lines 33 and 39 and an intermediate valve 55controlling the lines 45 and 46 in order to facilitate reversing thefurnace at the end of each regenerative cycle. The steam lines 34, 4|,49 and 50 are similarly connected to a central line 56 supplied withhigh pressure steam to atomize the fuel oil (compressed air may besubstituted for steam). A valve 51 and by-pass valves 58 and 59 controlthe flow of steam to the lines 34 and 4| and corresponding valves 60, 6iand 62 control the flow of steam to the lines 49 and '50 in order tofacilitate reversing the furnace at the end of each regenerative cycle.The above mentioned valves in the fuel oil and steam supply lines mayalso be controlled to turn off the supply of fuel oil and steam when thegas burners are turned on to heat the furnace. The gas burner supplylines are likewise controlled by valves (see valves I 'lb and I8!) inFigure 2) in order to reverse the furnace for regenerative purposes andin order to turn off the gas burners when the oil burners are turned onand vice versa.

During operation of the furnace the gas burners are employed when gas isavailable to heat the furnace and during this period the oil burners aredisconnected from their supply lines and are pu led back out of the airpassages at each end of the furnace. However, when it is desired to heatthe burners with fuel oil alone, the oil burners are inserted into theair passages as illustrated in Figure 2, the fuel oil and steam supplylines are connected to the oil burners, the control valves are adjustedto supply fuel oil to the burners and steam to atomize the fuel oil. andthe oil burners are adjusted laterally as shown in Figure 2 and arerotated about their axes as shown in Figure 1 until the cones of fireare properly adjusted to heat the charge in the furnace and to avoidinjury to the furnace lining. The cones of atomized fuel oil should beso directed that they do not play against the walls of the.,surroundingpassage nor against the edges of the port or of the roof knuckle at theend of the passage. It is also of importance that the separate identityof the flames from the several burners be maintained at least until theyare beneath the adjacent roof knuckle.

When we is again available to fire the furnace the gas burners are againturned on and the fuel oil burners are disconnected and pulled back outof the air passages at each end of the furnace. It is thus apparent thatmy system of burners provides two heating systems in the same furnacewhich can be used optionally to heat the furnace with gas alone or oilalone and can be alternated while keeping the furnace in continuousoperation.

In the drawings, I have shown a furnace with two oil burners at eachend. In some cases it may be desirable to use three or more burners butin any case the separate identity of the separate flames should bemaintained at least until the names are beneath the adjacent roofknuckle.

A great advantage of my invention lies in the fact that suitabletemperatures for melting down and refining can be maintained in theworking chamber of the furnace and that highly satisfactory operatingconditions are obtained with oil fuel despite the fact that the chamberis shaped for gas firing. A notable ,consequence of the use of myinvention is that the life of the brickwork is not diminished as hasbeen the case heretofore when it was attempted to use straight oil in afurnace of gas-fired design. I desire particularly to point out thatcontrary to what might be expected, the preservation of the brickwork ateither end of the furnace results from the observation at the other endof the furnace of the principles herein disclosed. In other words, theimpairment of the brickwork if these principles are not observed will befound to take place at the exit end of the furnace.

Although I have illustrated and described a preferred embodiment of theinvention, it will be recognized that changes in the arrangements anddetails may be made without departing from the spirit of the inventionor the scope of the v appended claims.

I claim:

1. An open hearth regenerative furnace of gas-fired design comprising acentral melting chamber with a roof, a down-sloped and progressivelynarrowing air passage leading into each end of the melting chamber andterminating in a port spaced substantially below theprincipal level ofthe roof, well-defined roof knuckles over each of said ports andcontrolled means for supplying gaseous fuel to each passage for normalgas-fired operation, in combination with an oil combustion system foruse when gaseous fuel is unavailable comprising at least we burners foreach end of the furnace, controlled means for supplying fuel oil and acompressed gaseous medium to each burner, each burner having a nozzlefor releasing a conical stream of oil atomized in said gaseous mediumand the several nozzles at each end of the furnace being positionedwithin the respective air passages and directed toward the centralmelting chamber, the nozzles in each passage being oppositely spacedfrom each other, from the interior surfaces of the passage, and from theport at the end of the passage so that their cones of atomized fuel willmerge only after passing beneath the knuckle into the central meltingchamber.

2. An open hearth regenerative furnace of gas-fired design comprising acentral melting chamber with a roof, a down-sloped and progressivelynarrowing air passage leading into each end of the melting chamber andterminating in a port spaced substantially below the principal level ofthe roof, well-defined roof knuckles over each of said ports andcontrolled means for supplying gaseous fuel to each passage for normalgas-fired operation, in combination with an oil combustion system foruse when gaseous fuel is unavailable comprising at least two burners foreach end of the furnace, controlled means for supplying fuel oil and acompressed gaseous medium to each burner, each burner having a nozzlefor releasing a conical stream of oil atomized in said gaseous mediumand the several nozzles at each end of the furnace being positionedwithin the respective air passages and directed axially parallel to eachother toward the central melting chamber, the nozzles in each passagebeing oppositely spaced from each other, from the interior surfaces ofthe passage, and from the port at the end of the passage so that theircones of atomized fuel will merge only after passing beneath the knuckleinto the central melting chamber.

3. An open hearth regenerative furnace of gas-fired design comprising acentral melting chamber with a roof, a down-sloped and progressivelynarrowing air passage leading into each end of the melting chamber andterminating in a port spaced substantially below the principal level ofthe roof, well-defined roof knuckles over each of said ports, a pair ofgas burners directed toward each other from opposite sides of eachpassage, and controlled means for supplying gaseous fuel to said gasburners for normal gas-fired operation, in combination with an oilcombustion system for use when gaseous fuel is unavailable comprising atleast two oil burners for each end of the furnace, controlled means forsupplying fuel oil and a compressed gaseous medium to each oil burner,each oil burner having a nozzle for releasing a conical stream of oilatomized in said gaseous medium and the several nozzles at each end ofthe furnace being positioned within the respective air passages anddirected axially parallel to each other toward the central meltingchamber, the nozzles in each passage being positioned below the level ofthe roof knuckles and at the level of the adjacent gas burners and beingpositioned between the adjacent gas burners and the adjacent port, andsaid nozzles in each passage being oppositely spaced from each other,from the interior surfaces of the adjacent passage, and from the port atthe end of the passage so that their cones of atomized fuel will mergeonly after passing beneath the knuckle into the central melting chamber.

FREDERICK S. BLOOM.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,506,840 Kernohan et a1. Sept.2, 1924 1,564,049 Davies Dec. 1, 1925 1,964,774 Smoot July 3, 1934

